Garmin FR310/910XT Trail Test

Original Review date: June 2016.

Summary

Yes, this review is a few years late with respect to release date. But these suckers remain relevant on the trail and are still the best Garmins we’ve tested in terms of distance accuracy and battery endurance (as of June 2016). Aside from elevation the FR310XT and FR910XT are similar enough in accuracy and functionality to combine the review. These two fill the core needs of a trail runner very well. Though they do have days where they lose the positional plot and put you +20m off the side.

A current model round-up can be seen here, and the testing methodology is here

What kind of trail runner is it good for?

Someone who already owns one, as we’re not sure if they still sold new anywhere. Second hand they’d be an excellent bargain for runners on a budget (though battery life might be comprimised this many years on). The two would suit any trail racer up to the 100km distance for sure, and with the barometer the 910XT is the model choice for those heading into the hills.

What should you expect as a long term running companion?

No real dramas, though prone to a bit of erratic/imaginary tracking (this doesn’t unduely effect distance accuracy). You might suffer a bit of envy from more recent ‘smarter’ models but these newer models could actually be a downgrade in accuracy (kind of like your 3rd wife).

Good Stuff

Accurate most of the time, great real world battery life, good strong vibrate function, highly legible screen (and flexible screen setup). Decent core feature set for trail runners. Can do Android syncing via 3rd party apps. Able to overide GPS with footpod. Nice responsive button and interface for runners.

Bad Stuff

No wrist based cadence, painfully slow GPS acquisition time (compared to modern GPS), can’t be used as normal day to day watch. They positionally spack out from time to time (though not enough to adversely effect long term performance). The 310XT was known to break straps at inopportune time, saw a guy double back after race start to retrieve his from the bush. And the 910XT had issues with screen fog. 310XT had no barometer making elevation a bit of a lottery.

Plea to Garmin

Make your modern trail capable GPS models at least as good as these in regards to real world battery endurance and distance accuracy.

Formal Testing

Accuracy

So far the forerunner testing has covered in excess of 300km on the surveyed courses over +30 separate days (repeated testing is vital to capture variation). A number of the activities were also specifically planned to assess the impact of poor satellite coverage (via tools that give geometric dilution of precision or GDoP). Potential GDoP was logged for every activity to better make comparisons across models.

The GPS pool against which the 310XT/910XT were tested included the following models: Suunto Ambit2, Suunto Ambit3 Peak, Polar V800, Garmin fēnix 2, and Garmin fēnix 3.

During testing multiple GPS devices are carried as a means of validation, if all units have a bad GPS day then a tin foil hat is donned. Though some days with poor GDoP potential saw all units a little degraded, no testing days saw GPS chaos across all models.

Positional

Positional accuracy, statistically is good if we use an average or median figure. But as already indicated both models lose it from time to time. In unobstructed GPS conditions the median offset was 1.7 metres (mean 2.5). In limited skyview conditions the forerunner XTs had a median offset of 2.4m (mean 3.6m). These figures put the positional accuracy in a respectible middle positon when compared to all other more modern units.

310XT/910XT distribution of accuracy against surveyed courses (the outliers actually go out to 77m)

When the forerunner XT’s were taken into genuinely difficult conditions (heavy tree cover, steep terrain, gorges), they performed rather better than the surveyed accuracy would have suggested. Mostly because the days in the rough weren’t among those erratic days seen. At a 5.4m average offset (4.4m median) they came in behind the Ambits but much better than the fēnixs, and pretty much identical to the Polar V800.

As might be expected variance in accuracy is high given their ‘where are we again?’ days. You’ve got no way of knowing if today is going to be a good track day or not. Still, poor track days were pretty infrequent.

Distance

Assessing true distance accuracy is not easy in trail conditions. GPS measured distance is dependent on positional accuracy and sampling rate. Unfortunately errors in positional accuracy can both increase and decrease distance via corner cutting and random scatter, and both are common in trail conditions. As these can cancel each other out an inaccurate track can still give spot on distances. A third type of error, shadowing, where the track is parallel generally has little effect on distance (unless it’s well off and converges).

With the forerunner XTs, overall distance accuracy over the surveyed course came in at a respectable 99.9%. So long term average, distance was excellent. On any given day you can expect recorded distance to be within 1% of the true surveyed distance 68% of the time which actually puts it in second place of all the models tested to date. Though you’ll also encounter the odd day which is well off.

In challenging GPS condition outings (ie. typical NZ bush conditions) the forerunner XTs invariably came in a little over the expected distances (up to 9%). Though the true course distances aren’t not known, tracks largely follow contours and features, though off-course shadowing is frequently seen especially against hard vertical faces. The tracks were also pretty zig-zaggy in places.

Track Appearance

Tracks under reasonable GPS conditions generally appeared pretty well aligned and responsive for the most part. There is a clear difference in the 1s versus smart recording mode with respect to track appearance. The smart mode is rather smoother, though still pretty responsive, whereas the 1s recoding can appear overly jagged especially under tree cover.

The trackpoint cloud image below shows the density of GPS position updates from all recorded runs against part of surveyed course. The relatively open sky view condition tracks are on the right, and the tricker conditions on the left. It’s pretty obvious there were some really bad days in there (seen both in the 310XT and 910XT). This didn’t seem to be connected to sky view conditions at all. Not clear what triggers them other the other units from the day didn’t encounter any such issues.

Combined FR310XT/FR910XT Track Cloud

Elevation

Here’s where the 310XT and 910XT start departing. The 310XT came in at a dismal 59% of total climb (and was also capable of recording 150% of actual climb), and the 910XT fared somewhat better at around 71%, still somewhat adrift of other models. Not sure if these results translate into more elevationally challenging terrain.

Note: The survey course probably is a bit tough on GPS watches with respect to elevation with lots of rapid 10-30m climbs/descents. Watches would probably perform better on longer more pronounced climbs/descents.

Battery Saving Data Recording

These older generation watches don’t have any battery saving/endurance mode. You can select 1s or smart recording. Smart recording is where data is saved less frequently if direction, speed, or heart range are unchanged.

Functional Tests

Data Syncing and Sharing

Pretty simple,plug in your ANT+ dongle and sync to Garmin which can sync with various services. Though at times it wasn’t simple, the forerunners flat out refused to upload some runs. Much fiddling, cursing, and forum reading generally resolved this. Painfull experience though.

Once uploaded recorded activities can be automatically synced to a number of 3rd party services via Garmin Connect. Additionally Garmin Connect allows services to sync non Garmin activities into Garmin Connect.

The files are also locally stored so you can do with them as you want. Garmin are admirably open in the data side of things. Nice. As a bonus you can even sync these with an Android device that has ANT+ (ie mostly Sony and Samsung).

Navigation Functions

Pretty simple here as well, you can follow previously recorded runs or other runs you can get via the Garmin Connect website. You get a basic breadcrumb map to follow with no waypoint alert functionality.

You can also navigate via a bearing to a saved waypoint. Though the watches don’t have an electronic compass so you only get a direction relative to your movement.

As mentioned, no electronic compass, and no formal trackback – though you can add a map screen to the watch and simply follow the recorded breadcrumb back to the start.

Pacing Functions

Both watches let you run against a fixed pace with an indication of how far in front or behind you are against the target pace. The 910XT also adds the Virtual Racer function where you race a previously recorded course that includes the actual pace of the previous run. The Vitrual Racer function is great for a bit of motivation or hitting PBs as the pace is realistic on the hills or tricky terrain.

Battery Run Down

During the high accuracy exhaustion trail test, the 910XT came out second from the pool at with 17% battery remaining after 15.5hrs. (the Ambit3 had 19% battery remaining). The run was done in warm conditions with about 50% open sky and 50% heavy bush. The 910XT was a few years old at the time of the test to boot. While the 310XT wasn’t on the test that day but we’ve been on plenty of ultra distance outings where they’ve gone the distance.

Standard Feature Set

General Trail Running

GPS accuracy under canopy : Good

Consistent GPS accuracy : Distance yes, position no

Rapid GPS Acquisition : No

HRM : Yes

Cadence option : Yes

Battery 8hr with HRM and high accuracy setting :

Barometer : FR910XT

Breadcrumb with waypoint navigation : No

Vibration alerts : Yes

Trail legible display: Yes

Open data access : Yes

Fully ANT+ or BLE Compliant : Yes

Ultra Feature Set (as per trail running plus)

Battery 14hr+ with HRM and high accuracy recording : Yes

Battery 24hr+ with HRM and down-sampling : No

Electronic compass : No

Nice to Have Features

Mobile uploads : Yes (via 3rd party Android app)

Cadence (without footpod) : No

HRV (R-R) recording with recovery estimate/test : No

Footpod GPS override : Yes

Basic interval workout ability : Yes

Pacing function : Constant (and FR910XT historic pace)

Position/waypoint autolapping : Yes

Custom timer reminders : Yes

Everyday watch : No

Activity Tracking : No

Mobile Notifications : No

Non-Tested Core Features

While functions like heart rate are core, either we’ve got no means of objectively testing them. Heart rate seem consistent with other models used, so no concern there. No other features really tested.

General Useability

Simple, and solid. You’ve got logical button placement and functions, a strong vibrate and loud alert. The watches sit a bit proud on the wrist and are liable to catch things, but no worse really than the Ambit or fēnix range. Then there’s that orange on the 310XT…

The custom workout function which can be setup on the watch or via Garmin Connect is simple enough and still works well. A nice way to introduce a bit of structure to your training. And as mentioned the follow course allows the race your historic self feature.

Where they fall down is the eternal wait for a GPS fix when you get started. You’d better you hope it’s not raining cos you’ll be wet by the time you can start running. And since you can’t wear them day to day theirs the chance you’ll have forgotten to turn them off on a previous run or neglected to charge them. And as well all know if it’s not digitally recorded, you didn’t run it.

Long Term Verdict

Great watches that have stood the test of time, those in the MEC bunch have done some thousands of km and have proven their reliability across a huge range of conditions. They certainly can go the distance no reliability concerns.

Yes, you’ll put up with some days where they truly lose the plot, though this effects the track location much more than the distance. And elevation on the 310XT is not to be taken too seriously, though the 910XT situation is somewhat improved with the barometer. It still falls a bit short of more modern units.

Look, if you have one and it’s still got a solid battery, you’ll want to look hard at what you are going to ‘upgrade’ to. There are certainly more recent models that would represent a backwards step with respect to real world battery life and distance accuracy.